A 12.5 Gb/s 0.13‐μm CMOS inductorless transimpedance amplifier with 1 pF input capacitance for optical communications

Abstract

Summary This paper proposes an inductorless fully differential transimpedance amplifier (TIA) with a single‐ended photo current to offer high bandwidth for applications of beyond 10 Gb/s optical communications. The presented TIA provides a much lower input impedance by modifying the cross‐coupled regulated cascode (CC‐RGC) configuration. The introduced method is able to enhance the bandwidth in the presence of wide range of input photodiode capacitance from small to large values, with a negligible increase in the peaking of frequency response. The proposed circuit is designed and simulated using the TSMC 130‐nm CMOS technology to validate the proposed technique. The post‐layout simulation results show that the TIA delivers a transimpedance gain of 46.5 dB normalΩ, a bandwidth of 8.8 GHz, and an input‐referred current noise of 33 pA/√Hz. The circuit occupies an active area of 0.004 mm2 and consumes 9.8 mW from a 1.3 V supply. Furthermore, the robustness of the proposed TIA is verified by means of the Monte Carlo simulations.

An improved low‐input resistance folded‐cascode transimpedance amplifier for giga‐bit per second optical communication front‐ends

“…By comparing (3), (5), and (12), the compromise between the input resistance, transimpedance gain, and frequency bandwidth becomes clear. M5 shows its importance for manipulating the gain and bandwidth product, as it appears in…”

“…Also, the role of g m1 is of high importance. Increasing the value of g m1 will decrease the input resistance (3) and the transimpedance gain (5) and increase the frequency bandwidth (12). Besides, by M1 transferring its thermal noise to the input node, any increase in the value of g m1 will increase the input-referred thermal noise of the TIA.…”

“…Along with the mentioned problems, the photodiode presents a rather large parasitic capacitance at the input node, significantly limiting the system's frequency bandwidth. By presenting a small input resistance, thus a small time constant, regulated cascode (RGC) structures [3][4][5][6] isolate this parasitic capacitance. However, such structures demand high voltage headroom for high data rates.…”

Employing bias current feedback in MIC transimpedance amplifier to increase bandwidth

“…Modified versions of the RGC structure have been proposed to overcome the headroom limitation and provide lower input impedance. [8][9][10][11][12][13][14] The other common topology to reduce the input impedance is to use the cross-coupled structure. 15 This structure is shown in Figure 1C.…”

“…Therefore, limited headroom is available for the effective voltage of M 2 or voltage drop across R D . Modified versions of the RGC structure have been proposed to overcome the headroom limitation and provide lower input impedance 8–14 …”